Control unit



Nov. 29, 1949 R. A. LEE 2,489,424

CONTROL UNIT Filed Dec. 11, 194s 4 Sheets-Sheet 1 FULERUM IN VEN TOR.

PWALQG. MZ5m4 Nov. 29, 1949 R. A. LEE 2,489,424

CONTROL UNIT Filed Dec. 11, 1943 4 Sheets-Sheet 2 I IVA l VII V i 56 /1 v 5 E 21 26 y,

Richardfl .Lee

ATTZZAWDK I N VEN TOR.

R. A. LEE

CONTROL UNIT Nov, 29, 1949 Filed Dec.

4 Sheets-Sheet 4 w ml A Md Patented Nov. 29, 1949 STATES PATENT OFFI CE,

CONTROILUNIT.

Richard A. IJee;,Bogta, NJJL', assignor to Bendix Aviatiomcorporation, Teterboro, N. J., a corporatiomofDelaware Application December 11, 1943, Serial No. 513,963;

2"(3laims. (Cl.'103"25) indicator-systems,.wherebyxpower for. driving a driven member, such as assuperchargerypump, blower or the :likezis interruptediintermittentlyaccording. to differentials -in. .pressur.e; to thereby control the speed of .the drivenzmember in pro,- portion to airspeed.

Another, object 1 is tQq provide novel improve ments: in control units. of 1 the: classiset forth; wherein a novel and simplified lever arrangement between the .conditionresponsive: members is designed, whereby, constantly gopposediorces are exerted on said simplifledl-lever-arrangement, so as tot-make orbreakva contactlassociated with said. lever. when pressures in said condition responsive members are unbalanced ,to. thereby energize. or

deenergize apowencircuit to control onesource of -,pressure and. rebalance the scondition respon-- sivemembers, and.therebwmakecontact to energizeor deenergizeesaidv .power..circuit.

Another object is to. provide a-novel condition responsive means. designed..for.use in combination withv a blower ortheJik'e and -an...electrical drivingmeans for the same, wherebya pressure;-

balance is maintained between the .blower.pres sure and a base pressure; such .asPitot pressure by constant regulation .of theblower speed.

Another. object is to provide .a. novel ..control= unitfora' true airspeed device including conditionresponsive means actuatedby pressure from.- aipower"driven.blower' or'tlie'like rotating in accordance with airspeedandiactuated by Pitot impact and static pressures," whereby, upon .varia- I tion" betweentblower *pressure' and L'Pitot impact and= static pressuresgpowertto .said blower is interrupted, sothat the speed"of'frotation of said blower or the like '-is':either increased ordecreased' to=- maintain said pressures proportional and.

thereby measurechanges "irnaifspeed Another object is tdprovideanix'nproved novel control meanshavingua:patriot pressure resporr- 2 site members actuated by different sources of pressure adapted to provide constantly opposed balanced moments of'force against a switch..ac= tuator means to maintain a circuit, until'. one source of pressure changes to unbalance said moments of force and the circuit is. thereby opened."

Yet" another object is to provide a novelfiuid actuated switch, which is simple in construction, instantly responsive ateither slow or rapid pressure changes, and more readily assembled" and adjusted in comparison With'oth'er devicesof'this type;

The above andother objects' and" advantages of" the present invention will appear more" fully hereinafter from a consideration-of the' detailed description which follows, taken-togethenwith" the accompanying drawings wherein one embodimentofthe invention is illustrated? Itis to be expressly understood, however, thatthe drawingsare for the purposeofillustration only' and are" not-designed as a-definitionof the-limits-of'tlie invention. Reference for this latter purpose' should be had to the appended claims.

.Inrthe drawings,- wherein like refrencecliar acters refer to like :partsth-roughout theseveral VIEWS,

Figure 1 is an explodedperspective-view of-an instrument .casing, part of the mechanism, and oiathe inside surface of a cover therefor.

Figure 2 is a perspective .view of the supportin-g frame for the units showing them mounted therein, which fits within the casing.

Figure 3 is a longitudinal cross section view 'of the frame showing a front view'ofthe control units attachedthereto.

Figure 4 is a longitudinal section view oil-"theframe. atrright angles to :Fig; Bishowing an edge view-of the diaphragms mounted in the frame Figure'5 is a longitudinal. side-elevationview, partly in section, of the diaphragm and controls: therefor mounted in the frame-of the opposite side to that of Figure 4.

Figure 6 is a diagrammaticview'illustiating the: points of applied moments of force.

Figure 7 is an end perspective view of avfrag ment of the frame showing details of the contacts v arrangement.

Figure..8 is a schematic wiring diagramof-thei pumpand motor showing the control thereof' byi" the leverisystem.

Referring .to the drawings in detail-,-,and-'-1in particular to Figure 1, the entire device is en'+-== closedin a casing J which is made-airtight bfiprovidedgwithl a -top: or -coverr| [having an: eleGs-i trical outlet plug [2 in circuit with a contact 26 or terminal wires on an insulation contact support plate 13, best shown in Figure 7, and a suitable power circuit illustrated in Figure 8, adapted to drive an electric motor 50 in driving connection with a mechanical source of pressure supply, such as the compressor 5|, more Iuliy shown and described in co-pending application Serial No. 512,013 filed November 27, 1943, now Patent 2,441,381, May 11, 1948, and assigned to the assignee of the present invention.

In the bottom of casing in are provided three openings, in which are coupled. tubes l5, l6 and I1. Tube is connected to the static inlet of the usual Pitot tube 53 (Figure 8) and discharges into the interior of the casing III, while tube It conveys the Pitot impact pressure into a diaphragm 18 mounted in frame l9 and tube ll conveys pressure output from a compressor 5| into a diaphragm 20 mounted in frame I9, see Figure 4.

Frame 19 comprises a head plate 2! adapted to be secured to the under side of cover II by lugs 22, 23 and 24. Plate 2| is also drilled, so as to provide apertures for wire 25 from the contact 26 and for taper screw adjustment 21, said screw 21 having a threaded bearing in the frame l9 and supported in contact with anvil 21a of resiliently mounted contact 26, as shown in Figures 5 and 7.

Extending from head plate 2| are standards 28 and 29, as shown in Figure 4, which are spaced apart and substantially parallel to each other, and held stable by members 30 and 3|, adapted to bridge part of the space adjacent each end of standards 28 and 29.

Bridge member 30 is drilled through at opposite points midway between standards 28 and 29 to receive reduced ends 32 and 33 of rock shaft 34, see Figure 3. Rock shaft 34 extends across the bridge member 30 at right angles to standards 28 and 29 and has secured thereto a balance lever 35 and a balance weight 35a radially adjustable on a rotatably adjustable arm 35b. Weight 35a counterbalances the weight of the lever 35 about the rock shaft 34.

The balance lever 35 is so positioned, proportioned and shaped as to extend between the two dlaphragms l8 and 20, which diaphragms are provided with force applying loops 36 and 31, see Figures 4 and 5, that are always in contact with the lever.

Loop 36 contacts lever 35 at point Fm below and at one side of shaft 34, while loop 37 contacts lever 35 at point F on the side opposite to point F, see diagram Figure 6.

Diaphragm I 8 is mounted on a shaft or post 38 seated in block 39 secured to standard 28 by screws 40 and diaphragm 20 is similarly mounted on a shaft or post 38 seated in block 4| on standard 29. One or both of the blocks may be mounted, so as to be adjustable longitudinally of the standard to which it is attached, such as shown in connection with standard 28, Figure 4, which is provided with elongated screw holes 42, as shown in Figure 2, to permit such adjustment.

The diaphragm I8 is connected through its mounting in its post hub or stud to the impact pressure line l6 from a suitable Pitot tube 53 and diaphragm 20 is connected similarly in the compressor output line H, so that diaphragm I'8 exerts force at point Fm and diaphragm 20 exerts force at point F on opposite alternate sides of ever 33. The points Fm and F at which the diaphragms l8 and 23 contact the lever 35 through the medium of the loops 36 and 31, are spaced apart near the fulcrum or shaft 34 and near the free or outer end of the lever 35, to establish a predetermined differential between said forces or pressures in accordance with any variation desired and to maintain a normal balance under such predetermineddifferential or proportion. The points Fm and F on the lever 35 correspond to the points of application of power and weight, respectively, on a lever of the second kind; the power in this case being the lower pressure of bellows 2U offsetting the weight as represented by the higher pressure of bellows 18, the rock shaft 34 being the fulcrum of the lever. The pressure in bellows 26 is approximately one-ninth that in bellows I8.

Secured to rock shaft 34 is an elongated contact arm 43 having a :contact 44 grounded to frame l9 through shaft 34 and terminal 43a while a stopscrew 43b limits and adjusts the movements of lever 35and arm 43, see Figures 2 and 7, to thereby cooperate with contact 26 of plate [3 in the power circuit to the compressor drive motor 5!].

Contact support plate l3 for contact 26 is secured to a bar 45 resiliently attached to standard 28 by suitable means, such as leaf spring 46 and is adjustable against the action of spring 46 shown in Figure 7, if desired by turning taper screw 21 in contact with anvil 21a on bar 45.

Operation Having thus far described the several elements of the device, brief reference is now made to the operation of the device.

Assume for example, the device is mounted on an aircraft, in a system for true airspeed and air mileage indication with the diaphragms l8 and 23 and parts within casing [0 subject to prevailing static pressure from'tube I 5 by connection to the static inlet of the usual Pitot tube not shown, and that speed of the craft is suddenly increased to unbalance the moments of force F and Fm. Such speed increase is instantly transmitted to the control diaphragm I8, to expand the latter by an increase in impact Pitot pressure through line I6 and an added force is applied to lever 35 and point Fm, whereupon the balance normally holding contact 44 of arm 43 away from contact 26 is overcome by an unbalancing of the forces so that lever 35 moves and closes contact through arm 43 between contacts 44 and 25. As the contacts 26 and 44 are closed a circuit from battery 52 is completed to the compressor drive motor 50 and a pressure established in diaphragm 23 through the compressor output line H proportional to the stepped-up pressure of diaphragm I8.

When the pressure in diaphragm 26 is proportional to the pressure in diaphragm l8, a condition of equilibrium exists and forces applied at F and Fm are balanced, contacts 26 and 44 are broken by opposite movement of the lever 35 and arm 43 with the shaft or fulcrum 34 assisted by the balancing weight 35a, and the compressor circuit is deenergized. This condition of equilibrium is maintained by the continued intermittent repetition of. the, above described operating cycle by increase of the pressure in the diaphragm l8 and expansion thereof. 1

There is thus provided a novel pressure actuated controladapted to, intermittently make and break a power circuit, so as to maintain a balance between the output pressure of an electrically driven air compressor or the like and Pitot tube impact and static pressure outputs, so as to accurately provide for true airspeed and mileage computations even at excessively high speeds.

Although the present invention is only described and illustrated in detail for one embodiment thereof, it is to be expressly understood that the same is not limited thereto. Various changes may be made in design and arrangement of the parts of the device illustrated, as will now be apparent to those skilled in the art. For a definition of the limits of the invention, reference should be had to the appended claims.

I claim:

1. A control unit comprising two pressure responsive members, a lever pivoted about a fulcrum at one end and acted upon by said pressure responsive members; said pressure responsive members acting upon said lever at unequal moment arms on the same side of the fulcrum to normally balance said lever; a source of dynamic pressure affecting the pressure member acting on the shorter moment arm of said lever, a compressor supplying the pressure affecting the member acting upon the longer moment arm of said lever, a switch adapted to be closed upon unbalance of said lever by an increase in the dynamic pressure, a motor adapted to operate said compressor, and a circuit including said motor and said switch to operate said motor upon switch closure to operate said compressor for increasing the pressure delivered thereby to its respective pressure responsive member to rebalance said lever.

2. A control unit comprising two pressure responsive members, a lever pivoted about a fulcrum at one end and acted upon by said pressure responsive members; said pressure responsive members acting upon said lever at unequal moment arms on the same side of the fulcrum to normally balance said lever; a source of dynamic pressure affecting the pressure member acting on the shorter moment arm of said lever, a coma pressor supplying the pressure affecting the member acting upon the longer moment arm of said lever, a fixed contact, a contact movable with said lever adapted to engage said fixed contact upon the unbalance of said lever, a motor adapted to operate said compressor, a circuit including' both of said contacts and said motor to operate said motor upon engagement of said contacts for operating said compressor to increase the pressure delivered thereby to its respective pressure responsive member for rebalancing said lever, and camming means associated with said fixed contact for varying the degree of unbalance required before said movable contact engages said fixed contact.

RICHARD A. LEE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 574,846 Freeman Jan. 5, 1897 1,007,178 Billings Oct. 31, 1911 1,201,660 Weatherhead et al. Oct. 17, 1916 1,240,790 Bristol Sept. 18, 1917 1,451,064 Dunajeff Apr. 10, 1923 1,698,692 Durdin Jan. 8, 1929 1,744,684 Grifiith Jan. 21, 1930 1,847,086 Gargan Mar. 1, 1932 1,942,913 Beggs Jan. 9, 1934 1,987,466 Collin Jan. 8, 1935 2,031,502 Powell Feb. 18, 1936 2,063,613 McCarthy Dec. 8, 1936 2,116,960 Brown et a1 May 10, 1938 2,269,069 Corbin Jan. 6, 1942 2,297,706 Jehle et al. Oct. 6, 1942 2,376,142 Hofiman et a1 May 15, 1945 FOREIGN PATENTS Number Country Date 352,702 Great Britain July 16, 1931 571,753 France 1 Feb. 8, 1921 

